Objective: To determine whether treatment of severe ovarian hyperstimulation syndrome (OHSS) with high-dose gonadotropinreleasing hormone (GnRH) antagonist, due to its luteolytic effect, is an effective method of management. Methods: Six infertile patients who had been scheduled for embryo transfer and developed early-onset severe OHSS with ascites and hemoconcentration were chosen for treatment with 3.0 mg of a GnRH antagonist (Cetrotide; Cetrorelix, Serono, Madrid, Spain). The response of these patients was compared with five patients with severe early-onset OHSS who received support therapy alone. All patients were evaluated clinically, echographically, and hematologically. Results: Estradiol (E2) levels dropped significantly a few days after treatment. Peritoneal fluid regression measured by ultrasound was faster on the study group compared with controls. Hematocrit remained comparable in both groups during follow-up. In two cases a second bolus of GnRH-antagonist was used due to clinical and biochemical findings during the four days of observation following the initial dose. None of the patients treated with GnRH antagonists required paracentesis. Conclusions: Treatment with high doses of GnRH antagonists seems to be effective in the management of severe OHSS.